The present invention pertains to a cement additive comprising a cement additive and to cementitious materials containing such an additive. The additive contains at least one alkanolamine or its salt, and at least one ionic functional group other than hydroxyl group.
Various substances have been known previously as agents for enhancing the strength of cement cured products, such as mortar and concrete, in which portland cement, mixed cement, etc., has been used. For instance, higher trialkanolamines, such as triisopropanolamine, N,N-bis-(2-hydroxyethyl)-N-(2hydroxypropyl)amine, tris-(2-hydroxybutyl)amine, etc., have been suggested. (See e.g., Japanese Kokai Patent No. Hei 3(1991)-183,647). The term xe2x80x9chigher trialkanolaminexe2x80x9d as used herein means and refers to a tertiary amine with at least one C3-C5 hydroxyalkyl group. Moreover, it is said that the strength of this cured product at ages of 7 days and of 28 days was enhanced by adding this trialkanolamine to mixed cement containing at least 4% C, AF, gypsum, and 5 to 80% filler or clinker base.
The above-mentioned higher trialkanolamines as used in the prior art contains a strong balance in their molecules between the hydrophilic hydroxyl and tertiary amine groups and the hydrophobic alkylene groups (a so-called hyidrophilic-hydrophobicbalance) and exhibits foamability in cement compositions. Consequently, if large quantities of higher trialkanolamines are used, the amount of air in the cured cement material product tends to be high. Therefore, a problem arises in that, even though the strength of the cement cured product has been enhanced, neutralization may be promoted by the increased amount of air, or long-term durability may be reduced due to salt damage or other factors.
Reducing the amount of air entrainer and adding anti-foaming agents during concrete manufacturing processes have been considered as a sort of solution to this problem. However, when a large amount of higher trialkanolamine is added, there is difficult in adjusting the amount of air entrainer and anti-foaming agent to coincide with this amount. Consequently, the first problem to be solved by the present invention is to provide a strength-enhancing agent to replace conventional higher trialkanolamines.
Another problem solved by the present invention is to provide a cement material that is dense and with which neutralization is delayed and there is good long-term durability.
As a result of proceeding with various studies of the above-mentioned problems, the inventors discovered that air entrainability can be improved and the short-term and long-term strength of the cement cured product can be increased when the additive for cement materials that is added is not simply an alkanolamine, but rather an alkanolamine that has at least one ionic functional group other than a hydroxyl group.
The present invention was completed based on this knowledge. The above-mentioned first problem is solved by additives for cement materials comprising at least one alkanolamine or its salt or derivative (e.g., ester) and at least one ionic functional group other than a hydroxyl group. In particular, the above-mentioned problem is solved by additives for cement materials selected from alkanolamines at least having one ionic functional group other than a hydroxyl group, and such alkanolamines may comprise at least two alkanol groups such as in, for example, trialkanolamine or monoalkyl dialkanolamine or their salts or derivatives.
Furthermore, it is preferred that the ionic functional groups be selected from, for example, the following: carboxyl groups, sulfonic acid groups, dicarboxylic acid monoester groups, and sulfonic acid monoester groups. The problem addessed in the present invention is further solved by additives for cement materials selected from compounds represented by the following general formula (I) and their salts: 
wherein R1 and R2 are a hydrogen atom or alkyl group with 1 to 3 carbons (preferably a hydrogen atom or methyl group) and R3 is a 2-carboxylalkyl group (The alkyl group has 2 to 4 carbons, and is preferably an ethyl group or a propyl group.), hydroxycarboxylalkyl group (The alkyl group has 2 to 4 carbons, and is preferably an ethyl group or a propyl group.), 2-sulfoalkyl group (The alkyl group has 2 to 4 carbons.), or hydroxysulfoalkyl group (The alkyl group has 2 to 4 carbons, and is preferably an ethyl group or propyl group.). Furthermore, it is preferred that R3 in general formula [I] be a 2-carboxyethyl group, 2-hydroxy-2carboxyethyl group, 2-sulfoethyl group, or 2-hydroxy-3-sulfopropyl group.
Moreover, the problem addressed in the present invention is solved by additives for cement materials selected from compounds represented by the following general formula [II] and their salts: 
wherein R is a vinylene group, phenylene group or alkylene group with 2 to 6 (and more preferably 2 to 4) carbons.
Moreover, the problem addressed in the present invention is solved by additives for cement materials selected from the group of compounds represented by the following general formula [III] and their salts. 
Furthermore, the salts of the above-mentioned compounds are preferably alkali metal salts, such as sodium or potassium salts, ammonium salts, or alkaline-earth metal salts such as calcium and magnesium salts. Moreover, the above-mentioned second problem is solved by a cement material characterized in that it contains at least the above-mentioned additive for cement materials and cement.
In addition, the problem addressed in the present invention is solved by cement material characterized in that it contains at least the above-mentioned additive for cement materials, as well as aggregate, and cement. Furthermore, the object of the present invention is accomplished by cement material which is characterized in that in addition to the above-mentioned components, it contains concrete admixture. The lower limit of the content of the above-mentioned additive for cement materials (weight ratio to total weight) is 0.001 wt %, preferably 0.01 wt %, while the upper limit is preferably 0.2 wt %. That is, if less than 0.001 wt % additive of the present invention, which is too small an amount, is added, there will be little effect in terms of enhancing strength. In contrast to this, more than 0.2 wt % can be added, but the improvement in terms of enhancing strength will not be high and the cost will increase.
Moreover, the above-mentioned additive for cement materials can be added during the cement manufacturing process. It can also be added during the cement admixture or concrete admixture manufacturing process. In addition, it can be added during the cement paste, mortar or concrete production process.